1. Field of the Invention
The present invention relates to a touch-sensitive screen and a touch-sensitive device using the same.
2. Background of the Related Art
Nowadays, the touch-sensitive devices can be divided into four basic categories: resistance touch-sensitive device, capacitance touch-sensitive device, infrared ray touch-sensitive device and surface acoustic wave touch-sensitive device; wherein, the resistance touch-sensitive device is with lowest cost and is mostly widely used.
The resistance touch-sensitive devices can be categorized to: four wires, five wires and other types of touch-sensitive devices based on the number of the derived wires. A resistance touch-sensitive device comprises a screen and a touch-sensitive device controller. FIGS. 1, 2A and 2B show the basic structure of a five wires resistance touch-sensitive screen. As shown in FIG. 1, said five wires resistance touch-sensitive screen comprises an insulating substrate 2, a rectangular conducting layer 3 formed on the said insulating substrate 2, and a conductive coat 5 formed on said conducting layer 3 wherein, said conductive coat is separated from said conducting layer by a spacer layer 4. As shown in FIG. 2A, the five wires resistance touch-sensitive screen further comprises four conducting layer electrodes 6 located in the four corners of the conducting layer 3.
Further, as shown in FIG. 2B, a conductive coat electrode 6′ is derived from the conductive coat 5 to be used as a probe to measure voltage. Since there are five wires to be derived for the five electrodes in this type of touch-sensitive device, it is also called five wires resistance touch-sensitive device; wherein, said conducting layer 3 is a precise resistance net, and four conducting layer electrodes 6 are derived from four corners of the conducting layer 3. While a voltage is loaded on the X direction and Y direction of the conducting layer 3 respectively via the conducting layer electrode 6, different parts of the conducting layer 3 have different electric potentials corresponding to their locations. As shown in FIG. 3, while a touch action is generated, said conductive coat 5 is electrically connected to the conducting layer 3. At this time, said touch-sensitive controller loads a voltage to the X direction and the Y direction of the conducting layer 3 respectively via the conducting layer electrode 6. Said touch-sensitive controller further obtains the electric potentials in X and Y directions of the touching point via the conductive coat electrodes 6′ on the conductive coat 5, and exports the obtained potentials via the conductive coat electrodes 6′ on the conductive coat 5 to calculate the coordinates of the touching point.
However, the conventional five wires resistance touch-sensitive device has a typical technical bottle neck, the pillow distortion caused by the edge effects. The conventional five wires resistance touch-sensitive device has four conducting layer electrodes 6 located in the four corners of the conducting layer 3 to load the voltage, and the distance between the conducting layer electrodes is large. As a result, the electric filed lines are not evenly distributed; the equipotential lines are thus bent and eventually cause pillow distortion. A distribution of the pillow distortion equipotential lines is denoted in real lines in FIG. 4. The pillow distortion will make it difficult to estimate the touching point location at the edge of the touch-sensitive screen and will be a disadvantage to miniaturize the five wires resistance touch-sensitive device. There have been solutions in the prior art to correct the linearity of the equipotential lines to some extent, such as precise resistance net wiring, programmable system to regulate the resistance net wiring, sixth order compensation algorithm etc. However, the above mentioned correction methods are complicated, operation capacity consuming and high cost.